First I sketched the main scheme of my concept on paper. While I was sketching, the details were ignored so far as well as the fish.
Therefore at first I concentrated on the fish tank itself and the stand.

To get started, I will give a short reason for choosing different objects in my scene. First my thoughts were circling around common and boring rectangular fish tanks, which are often seen in different places. As I have been seeing these types of fish tanks since my childhood, they were not as attractive to me. I think rectangle tanks do not have anything special to catch people's eyes.

Therefore I chose a spherical tank. Then I thought that what if I place this thing on a marble stand? That will definitely give a classical look to the image.
Still I figured out without bubbles the fish won't last long. That's why I wanted my concept to be unique. To do this I thought of a plan that will recycle the water of that fish tank. That's why I thought of adding two pipes, one for pouring water and another for draining the same amount of water to keep the balance.

But that does not look nice either. So I changed a little part of my concept and converted one of the pipes in a snake like faucet rather than fitting a conventional tap at the end. And I realized pouring water on the surface would create sufficient amount of bubbles to keep the fish healthy.

I thought every aquarium has a light, which gives it a gloomy look. So in this case I thought uniquely again. I set a small spotlight at the center of the stand, which will project lights from within. I kept my backgrounds aside for the time being. I decided to keep the fish tank empty from other objects.